When driveshafts exceed about 65 inches in length, they have a tendency to vibrate and whip at high speeds of rotation. The longer the driveshaft, the more likely it is to vibrate or whip at high speeds. To overcome this problem, long driveshafts have sometimes been made from two short driveshafts, aligned and connected with a bearing. However, this aligned two part construction is very expensive.
A driveshaft made of two tubes, one within the other, according to the tube-in-tube concept of this invention, is much stronger and can be rotated at higher speeds without vibrating or whipping. The space between the tubes is filled with a lightweight dampening material which increases strength and further reduces the tendency to vibrate. As a dampening material, a lightweight foam is recommended, preferably polystyrene. The dampening material could also be made of other materials such as rubber, but a lightweight polystyrene is preferred. Such material dampens both vibration and noise. The dampening material is preferably injected into the space between the tubes in liquid form and allowed to foam and set.
One object of this invention is to provide a driveshaft embodying the tube-in-tube concept, having the foregoing features and capabilities.
Another object is to provide a driveshaft which is rugged and durable in use, can be made in greater lengths and operated at higher speeds without vibrating or whipping, and is capable of being readily manufactured.
A further object is to provide a method of making the driveshaft of this invention.
These and other objects, features and advantages of the invention will become more apparent as the following description proceeds, especially when considered with the accompanying drawings.